Simon Peyton-Jones wrote:
- A program that type checks can have its meaning changed by adding an
instance declaration
- Similarly adding "import M()" can change the meaning of a program (by
changing which instances are visible
- Haskell would need to be a lot more specific about exactly where
context reduction takes place.
I think all of these problems would go away if overlap was permitted within
a module but forbidden across modules. Are there uses of overlapping
instances for which this isn't flexible enough?
-- Ben
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